The present invention relates generally to devices for plumbing structural members and assemblies such as walls, beams, columns, door jambs, partitions and the like. Carpenters have always used plumbing devices, such as the conventional suspended pointed plumb bob, for establishing the position on a surface of a point which is unknown relative to a known point.
The conventional plumb bob usually includes a length of string from which a conical heavy bob weight is suspended so that the pointed tip is proximate to the floor or surface. Location of the proper spot is generally inaccurate since the bob weight will normally be from 5/8" to one inch above the surface and an estimate as to where it would touch the surface has to be made. With conventional bobs inaccuracies of from 1/16" to 3/16" are not uncommon.
Attempts have been made to utilize laser technology for precise accurate plumbing, however while such devices are highly accurate, they are large, complex and expensive. Various other attempts at optical plumbing devices have had limited success for specialized purposes. Note the following examples:
Abrams: U.S. Pat. No. 3,505,739
Lagasse: U.S. Pat. No. 3,909,952
Ohneda: U.S. Pat. No. 3,911,588
Benson: U.S. Pat. No. 3,988,837
Boyett et al: U.S. Pat. No. 4,106,207
Boyett et al: U.S. Pat. No. 4,206,550
All of these devices comprise sophisticated structure, not directly interchangeable by the general carpenter for the existing conical plumb bobs.